def save_images(mat_file, save_dir, new_im_name_tmpl):
  def deref(mat, ref):
    return mat[ref][:].T

  def dump(mat, refs, pid, cam, im_dir):
    """Save the images of a person under one camera."""
    for i, ref in enumerate(refs):
      im = deref(mat, ref)
      if im.size == 0 or im.ndim < 2: break
      fname = new_im_name_tmpl.format(pid, cam, i)
      imsave(osp.join(im_dir, fname), im)

  mat = h5py.File(mat_file, 'r')
  labeled_im_dir = osp.join(save_dir, 'labeled/images')
  detected_im_dir = osp.join(save_dir, 'detected/images')
  all_im_dir = osp.join(save_dir, 'all/images')

  may_make_dir(labeled_im_dir)
  may_make_dir(detected_im_dir)
  may_make_dir(all_im_dir)

  # loop through camera pairs
  pid = 0
  for labeled, detected in zip(mat['labeled'][0], mat['detected'][0]):
    labeled, detected = deref(mat, labeled), deref(mat, detected)
    assert labeled.shape == detected.shape
    # loop through ids in a camera pair
    for i in range(labeled.shape[0]):
      # We don't care about whether different persons are under same cameras,
      # we only care about the same person being under different cameras or not.
      dump(mat, labeled[i, :5], pid, 0, labeled_im_dir)
      dump(mat, labeled[i, 5:], pid, 1, labeled_im_dir)
      dump(mat, detected[i, :5], pid, 0, detected_im_dir)
      dump(mat, detected[i, 5:], pid, 1, detected_im_dir)
      dump(mat, chain(detected[i, :5], labeled[i, :5]), pid, 0, all_im_dir)
      dump(mat, chain(detected[i, 5:], labeled[i, 5:]), pid, 1, all_im_dir)
      pid += 1
      if pid % 100 == 0:
        sys.stdout.write('\033[F\033[K')
        print('Saving images {}/{}'.format(pid, 1467))